19
PALS Installation Manual
CRISIS CONTROLLER©™ HARDWARE (continued)
Coverage and placement of IRT Locators:
The guiding principle of installing IRT Locators
is that signals to PMTs will be unobstructed and
unambiguous. Wherever IRTs are used, the PMT
must be able to get ONE clear signal at a time. This
means that IRTs must be located in such a way that
users will always be in range of a PMT and that
signals from one IRT can always reach the PMT.
Several factors must be considered. First is range;
the effective transmission range of an IRT is a
function of its total peak output power. IRTs have
jumpers that permit users to use a low power
output, which reduces range. This is sometimes
desirable as a means of limiting overlapping fields
of coverage between adjacent receivers.
The next factor is location of the IRT device. Users typically carry PMTs on belts or service holsters. Signals to the
PMT can be shielded, or “shaded,” by the user’s body if the PMT is worn on the side of the user opposite the
location of the IRT. This situation is addressed by using sets of IRTs. IRT Slaves may be operated in conjunction with
IRT Masters. They transmit the same location data as the Master, at 5%-10% lower power. Strategically
placing these devices in an area guarantees that Locator signals can reach a PMT regardless of where the wearer is
carrying the PMT, or which direction the user is traveling. (If users must wear heavy protective gear, use of a Lapel
Reader with the PMT is
recommended.)
IRTs transmit data in 3-dimensions. Coverage may be envisioned as a “cloud” of signals through which the PMT
must pass. IRT signals disperse from their source, and are often augmented by signal reflection from most materials.
(Carpets and black surfaces are poor reflectors).
Installers should place IRTs to eliminate overlapping zones of dual coverage. When signals from adjacent IRTs
collide, “dead zones” are created, from which no viable information is accessible to the PMT.
IRTs are not affected by exposure to sunlight,
but PMT receivers can be saturated with
environmental IR and cannot read the Locators.
In these cases, installers should locate the IRTs in
areas that the PMT will not be in direct sunlight
when the Locator data needs to be received.
